1 00:00:49,549 --> 00:00:52,518 The high andes of Bolivia 2 00:00:55,155 --> 00:00:56,315 ln the 16th century 3 00:00:56,456 --> 00:00:58,117 rumours of fabulous Wealth 4 00:00:58,258 --> 00:01:01,853 dreW Spanish adventurers to this lonely place. 5 00:01:08,034 --> 00:01:11,731 What they found here exceeded their Wildest dreams. 6 00:01:20,380 --> 00:01:21,870 A mountain of silver... 7 00:01:22,015 --> 00:01:24,848 they called the Cerro Rico. 8 00:01:35,095 --> 00:01:39,156 To the Spanish the Cerro Rico Was a gift from God. 9 00:01:50,810 --> 00:01:53,802 The amount of silver Won from this mountain alone 10 00:01:53,947 --> 00:01:55,642 Was truly fantastic. 11 00:01:55,782 --> 00:01:59,513 Perhaps up to 60,000 tons of silver has been Won, 12 00:01:59,652 --> 00:02:02,120 enough to finance the entire Spanish empire, 13 00:02:02,255 --> 00:02:04,450 and indeed the Western World. 14 00:02:04,591 --> 00:02:07,651 lt is estimated that perhaps just as much remains. 15 00:02:07,794 --> 00:02:10,092 So that this mountain, Cerro Ricco, 16 00:02:10,230 --> 00:02:14,997 can truly be said to be the richest silver mine in the World. 17 00:02:17,003 --> 00:02:18,732 As over the centuries prospectors 18 00:02:18,872 --> 00:02:21,739 folloWed the trail of silver and also gold, 19 00:02:21,875 --> 00:02:23,433 it led them to rich deposits 20 00:02:23,576 --> 00:02:26,568 all round the great Pacific Ocean. 21 00:02:26,713 --> 00:02:29,443 ln fact, you might call the rim of the Pacific 22 00:02:29,582 --> 00:02:30,947 'The Ring of Gold', 23 00:02:31,084 --> 00:02:33,552 but it's more usually called 'The Ring of Fire' 24 00:02:33,686 --> 00:02:36,154 because all round the margin of the Pacific Basin 25 00:02:36,289 --> 00:02:38,382 associated With the mineral deposits, 26 00:02:38,525 --> 00:02:41,494 there are huge chains of volcanoes. 27 00:02:44,531 --> 00:02:46,328 At first sight, there might not seem to be 28 00:02:46,466 --> 00:02:49,833 any connection betWeen volcanoes and ineral Wealth, 29 00:02:49,969 --> 00:02:51,960 but in fact there is, 30 00:02:52,605 --> 00:02:54,402 and that link is a clue to one 31 00:02:54,541 --> 00:02:57,567 of the most puzzling mysteries about the earth. 32 00:02:58,244 --> 00:02:59,905 HoW did the dry land - 33 00:03:00,046 --> 00:03:02,310 the continents on Which We live - 34 00:03:02,448 --> 00:03:04,780 hoW did they form? 35 00:03:21,601 --> 00:03:25,264 Only one third of the Earth's surface is dry land. 36 00:03:26,472 --> 00:03:29,270 Most of the planet is covered by Water 37 00:03:34,347 --> 00:03:35,780 John DeWey is a geologist 38 00:03:35,915 --> 00:03:38,679 Who has spent his career looking at the rocks on land, 39 00:03:38,818 --> 00:03:41,309 trying to understand their origin. 40 00:03:43,656 --> 00:03:45,419 Those on the West coast of Scotland 41 00:03:45,558 --> 00:03:47,719 hold a special interest for him; 42 00:03:47,860 --> 00:03:50,420 they're the oldest in the British lsles. 43 00:03:52,865 --> 00:03:53,797 l think you have to remember 44 00:03:53,933 --> 00:03:56,458 that prior to about thirty years ago, 45 00:03:56,603 --> 00:03:58,195 geologists had been mapping the continents 46 00:03:58,338 --> 00:04:00,397 and making very detailed geological maps, 47 00:04:00,540 --> 00:04:02,701 over a period of perhaps a hundred years, 48 00:04:02,842 --> 00:04:04,434 including a beautiful map of this area 49 00:04:04,577 --> 00:04:06,670 made in the last century With exquisite details 50 00:04:06,813 --> 00:04:08,007 of all the rocks: 51 00:04:08,147 --> 00:04:10,138 but of course there Was no ready explanation 52 00:04:10,283 --> 00:04:15,220 to explain all these rocks and geological relationships. 53 00:04:16,222 --> 00:04:19,680 When John DeWey first came here over 30 years ago, 54 00:04:19,826 --> 00:04:22,124 many geologists still saW no distinction 55 00:04:22,262 --> 00:04:24,059 betWeen the rocks on dry land, 56 00:04:24,197 --> 00:04:26,427 and those beneath the sea. 57 00:04:26,566 --> 00:04:29,501 But that soon began to change. 58 00:04:32,538 --> 00:04:34,563 As scientists explored the oceans, 59 00:04:34,707 --> 00:04:37,267 they started to realize that the veil of Water 60 00:04:37,410 --> 00:04:38,968 concealed a fundamental difference 61 00:04:39,112 --> 00:04:42,445 betWeen the continents and the ocean floor. 62 00:04:45,318 --> 00:04:47,081 Unlike the continents, 63 00:04:47,220 --> 00:04:49,882 the deep ocean floor consists almost entirely 64 00:04:50,023 --> 00:04:52,719 of rocks of only one type. 65 00:04:54,894 --> 00:04:56,759 What's more, scientists Worked out 66 00:04:56,896 --> 00:05:00,354 that this rock had all been produced in the same Way - 67 00:05:00,867 --> 00:05:03,233 all erupted by undersea volcanoes 68 00:05:03,369 --> 00:05:06,167 that ran doWn the middle of the oceans. 69 00:05:09,909 --> 00:05:13,003 lt Was a beautifully simple picture. 70 00:05:16,549 --> 00:05:18,517 ln contrast, on the continents 71 00:05:18,651 --> 00:05:21,848 We see a very, very different kind of story. 72 00:05:22,989 --> 00:05:24,149 These rocks have suffered 73 00:05:24,290 --> 00:05:26,190 an immensely complicated histry 74 00:05:26,326 --> 00:05:27,850 over a very long period of time, 75 00:05:27,994 --> 00:05:29,461 in such a Way that these bands, 76 00:05:29,595 --> 00:05:30,687 light and dark bands, 77 00:05:30,830 --> 00:05:32,559 have been folded, sWirled together, 78 00:05:32,699 --> 00:05:34,098 squidged and squashed 79 00:05:34,233 --> 00:05:35,666 at very high temperatures and pressures 80 00:05:35,802 --> 00:05:37,064 in Ways that are typical 81 00:05:37,203 --> 00:05:38,830 in many many parts of the World, 82 00:05:38,971 --> 00:05:40,370 the kind of thing you see in the continents 83 00:05:40,506 --> 00:05:42,497 but never in the oceans. 84 00:05:42,642 --> 00:05:45,611 HoW had rocks like these been created? 85 00:05:45,745 --> 00:05:47,542 Unlike their ocean-going colleagues, 86 00:05:47,680 --> 00:05:50,171 land geologists lacked a simple theory 87 00:05:50,316 --> 00:05:53,308 that could explain the origin of the continental crust. 88 00:05:53,453 --> 00:05:55,353 ln those days, We didn't have it; 89 00:05:55,488 --> 00:05:58,082 We Were simply groping in the dark. 90 00:05:58,758 --> 00:06:00,225 The first glimmer of light 91 00:06:00,360 --> 00:06:01,691 came from the same region 92 00:06:01,828 --> 00:06:04,661 that had enriched the Spanish Empire... 93 00:06:06,299 --> 00:06:09,427 in the high Andes of Bolivia. 94 00:06:16,476 --> 00:06:17,670 Each year the people Who live 95 00:06:17,810 --> 00:06:19,277 at the foot of the Cerro Rico 96 00:06:19,412 --> 00:06:22,643 celebrate the source of their prosperity. 97 00:06:29,455 --> 00:06:30,615 But for many years the region 98 00:06:30,757 --> 00:06:33,521 has also attracted scientists like Rodney Grapes 99 00:06:33,659 --> 00:06:36,355 and Leonore Hoke from NeW Zealand. 100 00:06:37,163 --> 00:06:39,757 Top it up 101 00:06:44,103 --> 00:06:45,070 This year they're being joined 102 00:06:45,204 --> 00:06:47,502 by tWo British geologists... 103 00:06:47,640 --> 00:06:50,768 ...Rick Thomas and Catrin Jones. 104 00:07:02,388 --> 00:07:03,878 The team are heading for an area 105 00:07:04,023 --> 00:07:06,821 Which for thirty years scientists have suspected 106 00:07:06,959 --> 00:07:10,759 may hold the key to hoW the continental crust is formed.. 107 00:07:15,201 --> 00:07:16,532 OK, so Where are We heading? 108 00:07:16,669 --> 00:07:19,194 l think really We've got to go straight toWards that big volcano 109 00:07:19,338 --> 00:07:20,464 because there's nothing else 110 00:07:20,606 --> 00:07:22,301 that's gonna give us so good a bearing. 111 00:07:22,442 --> 00:07:24,876 So that's 3.10. 112 00:07:25,011 --> 00:07:27,844 We've got ...? behind us, to the right. 113 00:07:27,980 --> 00:07:29,208 We've got this distinctive volcano. 114 00:07:29,348 --> 00:07:31,578 Yes that's this one here. 115 00:07:31,717 --> 00:07:32,979 ... What is it - 3.10? 116 00:07:33,119 --> 00:07:34,484 We'll have to rely on your bearing then. 117 00:07:34,620 --> 00:07:36,588 OK, Well then let's go. 118 00:07:50,369 --> 00:07:52,929 Their journey takes them across the Salar, 119 00:07:53,072 --> 00:07:55,404 a dry salt lake... 120 00:07:55,541 --> 00:07:58,339 part of the vast Altiplano... 121 00:07:59,178 --> 00:08:03,512 a 4000 metre-high plateau in the middle of the Andes. 122 00:08:07,954 --> 00:08:09,182 There are the odd pot-holes, 123 00:08:09,322 --> 00:08:11,256 but l think it's the best road in Bolivia - 124 00:08:11,390 --> 00:08:13,688 you go flat out, 120 kilometres, 125 00:08:13,826 --> 00:08:14,850 if the car makes it. 126 00:08:14,994 --> 00:08:16,188 You're still going at sixty are you? 127 00:08:16,329 --> 00:08:19,662 Yeah, Well. Enjoy the vieW. 128 00:08:20,867 --> 00:08:23,927 BetWeen them and the Pacific coast lies their goal - 129 00:08:24,070 --> 00:08:25,697 a chain of active volcanoes, 130 00:08:25,838 --> 00:08:28,136 the highest in the World. 131 00:08:49,328 --> 00:08:51,193 As they near the volcanoes, 132 00:08:51,330 --> 00:08:53,662 the team start to see signs at the surface 133 00:08:53,799 --> 00:08:56,962 of tremendous activity deep beloW them. 134 00:09:09,348 --> 00:09:12,875 l'm familiar With the volcanoes in NeW Zealand, 135 00:09:14,353 --> 00:09:17,015 and it's a real thrill to come here to the Andes, 136 00:09:17,156 --> 00:09:19,488 Where you can see so many more of these volcanoes, 137 00:09:19,625 --> 00:09:22,355 very similar to the ones We have in NeW Zealand. 138 00:09:23,229 --> 00:09:25,163 The rock that's erupted from these volcanoes is 139 00:09:25,298 --> 00:09:27,528 in fact called Andesite, after the Andes, 140 00:09:27,667 --> 00:09:30,636 so if you like this is the home of the Andesite. 141 00:09:31,070 --> 00:09:32,867 Not just the volcanic cones, 142 00:09:33,005 --> 00:09:35,906 but the entire landscape here is made of andesite 143 00:09:36,042 --> 00:09:38,203 and other volcanic rocks. 144 00:09:38,344 --> 00:09:39,743 Since the 1960s, 145 00:09:39,879 --> 00:09:41,904 scientists studying the growth of the continents, 146 00:09:42,048 --> 00:09:43,106 like Rick Thomas, 147 00:09:43,249 --> 00:09:46,082 have been Working out hoW this happens. 148 00:09:56,162 --> 00:10:00,292 Volcanoes in the Andes are notoriously explosive. 149 00:10:02,969 --> 00:10:04,561 They can eject tons of ash 150 00:10:04,704 --> 00:10:08,231 and fragments of volcanic rock into the atmosphere. 151 00:10:09,609 --> 00:10:13,238 The reason for this behaviour is a surprising one. 152 00:10:18,017 --> 00:10:22,647 The liquid rock at depth contains a lot of Water, 153 00:10:22,788 --> 00:10:24,551 and that Water's happily dissolved 154 00:10:24,690 --> 00:10:25,884 When it's doWn deep: 155 00:10:26,025 --> 00:10:27,822 as it comes close to the surface, 156 00:10:27,960 --> 00:10:31,452 it froths up the magma, the liquid rock, 157 00:10:31,597 --> 00:10:32,894 and it causes it to explode, 158 00:10:33,032 --> 00:10:35,660 just like When you uncork a champagne bottle; 159 00:10:35,801 --> 00:10:37,701 same sort of thing's happening here. 160 00:10:37,837 --> 00:10:40,601 Froths up and What We get is fragments of rock 161 00:10:40,740 --> 00:10:42,765 Which are full of bubbles Within the rock 162 00:10:42,908 --> 00:10:44,102 and you get lots of these pumices 163 00:10:44,243 --> 00:10:46,268 Which you can see here. 164 00:10:47,980 --> 00:10:49,641 lf you'd been here during one of these eruptions, 165 00:10:49,782 --> 00:10:51,647 you'd have seen vast billoWing clouds 166 00:10:51,784 --> 00:10:53,308 in the distance coming toWards you, 167 00:10:53,452 --> 00:10:54,646 kilometres aWay, 168 00:10:54,787 --> 00:10:57,449 but in a minute or so, because they travel so fast - 169 00:10:57,590 --> 00:10:59,854 hundreds of miles an hour quite easily - 170 00:10:59,992 --> 00:11:01,482 they Would have engulfed you. 171 00:11:01,627 --> 00:11:03,891 and this ash cloud Would have just blasted on 172 00:11:04,030 --> 00:11:06,225 doWn the valley and just filled most 173 00:11:06,365 --> 00:11:08,833 of What We can see of that plain. 174 00:11:11,404 --> 00:11:13,736 As the clouds of ash and pumice settle, 175 00:11:13,873 --> 00:11:17,400 they compress together to form neW rock layers. 176 00:11:18,911 --> 00:11:22,608 Over time these layers gradually build up. 177 00:11:32,625 --> 00:11:34,684 Water is the key to this process 178 00:11:34,827 --> 00:11:36,761 and it's the Water that's attracted the team 179 00:11:36,896 --> 00:11:38,921 to this remote spot. 180 00:11:39,065 --> 00:11:40,965 Straight ahead of us, is OjagWe 181 00:11:41,100 --> 00:11:42,294 With its fumarole on top. 182 00:11:42,435 --> 00:11:45,097 Yes, a nice conical volcano, that, actually, and you can... 183 00:11:45,237 --> 00:11:47,228 Leonora plans to collect a gas sample 184 00:11:47,373 --> 00:11:50,206 from the active fumaroles at the summit, 185 00:11:50,342 --> 00:11:52,105 Which are continually producing steam 186 00:11:52,244 --> 00:11:53,541 and other vapours. 187 00:11:53,679 --> 00:11:55,510 ...quite clearly the fumarole there. 188 00:11:55,648 --> 00:11:58,116 As you come doWn the right shoulder, 189 00:11:58,250 --> 00:12:02,050 and you just might be able to make out lrruputuncu. 190 00:12:06,058 --> 00:12:08,049 And that's Where We're heading. 191 00:12:14,366 --> 00:12:15,765 Back in the Sixties, 192 00:12:15,901 --> 00:12:18,529 scientists searching for the origin of the continents 193 00:12:18,671 --> 00:12:20,536 realised that the explosive process 194 00:12:20,673 --> 00:12:23,073 they could see building up the landscape here 195 00:12:23,209 --> 00:12:25,473 Was not confined to the Andes; 196 00:12:25,611 --> 00:12:28,409 it Was happening elseWhere too. 197 00:12:33,586 --> 00:12:35,781 MattheW ThirlWall has collected rock samples 198 00:12:35,921 --> 00:12:38,913 from volcanoes all over the World. 199 00:12:39,391 --> 00:12:42,451 Of the thousand or so active volcanoes 200 00:12:42,595 --> 00:12:43,926 in the earth at the moment, 201 00:12:44,063 --> 00:12:47,590 some eighty per cent produce these highly explosive eruptions. 202 00:12:47,733 --> 00:12:50,702 This is a sample of pumice from the Andes, 203 00:12:50,836 --> 00:12:54,272 but We can find almsot identical pumice 204 00:12:54,406 --> 00:12:57,273 in several other places on earth. 205 00:12:57,977 --> 00:13:00,445 Here We have pumice almost exactly the same, 206 00:13:00,579 --> 00:13:02,410 With these gas bubbles in it, 207 00:13:02,548 --> 00:13:05,278 from Mount St. Helens in Washington State, 208 00:13:05,417 --> 00:13:09,478 and this is a typical example of Andesite, 209 00:13:09,622 --> 00:13:12,648 the characteristic rock in these areas. 210 00:13:12,792 --> 00:13:14,157 And you can see- 211 00:13:14,293 --> 00:13:17,057 find almost identical Andesites 212 00:13:17,196 --> 00:13:20,290 in several other recent eruptions - 213 00:13:20,432 --> 00:13:22,957 for example, here We have a sample 214 00:13:23,102 --> 00:13:25,434 from Mount Pinatubo in the Phillippines; 215 00:13:25,571 --> 00:13:27,334 very very similar samples 216 00:13:27,473 --> 00:13:31,500 With some four thousand miles of Pacific betWeen them. 217 00:13:31,644 --> 00:13:33,669 ln fact, geologists soon discovered 218 00:13:33,813 --> 00:13:37,112 that most of the volcanoes that surround the Pacific Ocean 219 00:13:37,249 --> 00:13:38,841 produce the same type of rock, 220 00:13:38,984 --> 00:13:41,509 in the same explosive fashion. 221 00:13:41,654 --> 00:13:45,181 We're completely safe from these eruptions in England, 222 00:13:45,324 --> 00:13:46,916 but if you happen to live anywhere 223 00:13:47,059 --> 00:13:49,391 near the edge of the Pacific Ocean, 224 00:13:49,528 --> 00:13:52,326 you can almost certainly drive Within a day 225 00:13:52,464 --> 00:13:55,592 to one of these Andesitic volcanoes. 226 00:13:57,036 --> 00:14:01,769 So the volcanoes of the Ring of Fire are all basically similar. 227 00:14:01,907 --> 00:14:04,307 Hundreds of them are continually erupting 228 00:14:04,443 --> 00:14:07,105 in an extraordinary arc that runs up 229 00:14:07,246 --> 00:14:09,077 the Western coast of the Americas 230 00:14:09,215 --> 00:14:13,345 from Patagonia all the Way to Alaska... 231 00:14:15,387 --> 00:14:19,585 And then continues all the Way around the Pacific Basin. 232 00:14:24,163 --> 00:14:27,098 lt daWned on scientists that in the process, 233 00:14:27,233 --> 00:14:29,201 the volcanoes Were building up a ring 234 00:14:29,335 --> 00:14:32,896 of Andesitic rock all around the Pacific. 235 00:14:37,476 --> 00:14:38,875 And then they discovered a link 236 00:14:39,011 --> 00:14:40,478 betWeen these rocks 237 00:14:40,613 --> 00:14:44,310 and those Which make up the continent as a Whole. 238 00:14:51,790 --> 00:14:53,621 As they analysed thousands of samples, 239 00:14:53,759 --> 00:14:55,226 from all over the World, 240 00:14:55,361 --> 00:14:58,592 a surprisingly simple picture emerged; 241 00:15:02,501 --> 00:15:04,128 though the rocks looked different, 242 00:15:04,270 --> 00:15:07,706 they Were made from basically the same ingredients. 243 00:15:07,840 --> 00:15:10,502 And indeed their average composition hardly varied 244 00:15:10,643 --> 00:15:13,578 at all from continent to continent. 245 00:15:15,281 --> 00:15:18,250 Even more significant, this average composition 246 00:15:18,384 --> 00:15:21,842 Was essentially the same as that of the volcanic rocks 247 00:15:21,987 --> 00:15:24,114 in the Ring of Fire. 248 00:15:27,927 --> 00:15:30,452 lf one Were to take all the continental crust 249 00:15:30,596 --> 00:15:32,996 of the Whole World, grind it up, 250 00:15:33,132 --> 00:15:34,690 then measure its average composition, 251 00:15:34,833 --> 00:15:37,461 it Would be very very similar to that of these rocks, 252 00:15:37,603 --> 00:15:39,833 and it Would consist of three basic minerals; 253 00:15:39,972 --> 00:15:42,702 the very translucent mineral is quartz, 254 00:15:42,841 --> 00:15:46,333 the rather milky mineral is felspar, 255 00:15:46,478 --> 00:15:49,879 and the dark green mineral is hornblende. 256 00:15:50,015 --> 00:15:51,539 And then if one goes to the Andes 257 00:15:51,684 --> 00:15:52,776 and looks at the volcanoes, 258 00:15:52,918 --> 00:15:55,216 and indeed looks at the rocks injected deep 259 00:15:55,354 --> 00:15:56,912 in the crust beneath the volcanoes, 260 00:15:57,056 --> 00:15:58,580 one has the same general composition 261 00:15:58,724 --> 00:16:03,024 as We find here, of quartz, of felspar and of hornblende. 262 00:16:03,162 --> 00:16:04,390 And of course that immediately 263 00:16:04,530 --> 00:16:06,327 begins to give one an inkling that possibly 264 00:16:06,465 --> 00:16:08,228 these rocks Were formed in the same Way. 265 00:16:08,367 --> 00:16:10,562 Andf not only that but much of the continental crust 266 00:16:10,703 --> 00:16:12,330 must have been formed in the same Way 267 00:16:12,471 --> 00:16:15,235 as We see in the Andes in the present day. 268 00:16:16,375 --> 00:16:18,434 So perhaps the continents had all been created 269 00:16:18,577 --> 00:16:20,204 by volcanoes like these, 270 00:16:20,346 --> 00:16:23,440 building up the crust over geological time. 271 00:16:24,583 --> 00:16:28,485 But, What Was creating the volcanoes themselves? 272 00:16:28,620 --> 00:16:30,679 And hoW could something happening around the Pacific 273 00:16:30,823 --> 00:16:33,883 explain the rocks in Scotland? 274 00:16:34,026 --> 00:16:36,517 All this Was a complete mystery. 275 00:16:39,431 --> 00:16:43,595 But then the Ring of Fire provided another vital clue. 276 00:16:43,736 --> 00:16:47,228 The region Was periodically rocked by earthquakes. 277 00:16:47,373 --> 00:16:48,863 ln 1964, 278 00:16:49,008 --> 00:16:52,239 a major one struck Alaska. 279 00:16:58,951 --> 00:17:02,387 l Was leaning in my cabin getting a cigarette, 280 00:17:02,521 --> 00:17:05,786 and all of a sudden it started shaking. 281 00:17:05,924 --> 00:17:09,724 We Was evidently right over the epicentre. 282 00:17:11,163 --> 00:17:14,394 These big sand spouts Were shooting up in the air. 283 00:17:14,533 --> 00:17:17,366 You can't believe hoW that boat shook and rattled. 284 00:17:17,503 --> 00:17:19,300 lt Was scary. 285 00:17:24,443 --> 00:17:25,569 Could l have your attention please? 286 00:17:25,711 --> 00:17:29,044 Alaska Airlines Flight 61 Will be arriving noW. 287 00:17:29,181 --> 00:17:30,614 The day after the earthquake, 288 00:17:30,749 --> 00:17:32,774 a US government geologist fleW in 289 00:17:32,918 --> 00:17:35,443 to investigate What had happened. 290 00:17:38,123 --> 00:17:41,286 George Plafker is still Working in the region. 291 00:17:41,794 --> 00:17:44,024 l Was in Seattle attending a geological conference 292 00:17:44,163 --> 00:17:46,131 When the earthquake struck. 293 00:17:46,265 --> 00:17:47,357 From the initial reports, 294 00:17:47,499 --> 00:17:49,694 We realised it Was a major disaster 295 00:17:49,835 --> 00:17:50,995 and a great earthquake, 296 00:17:51,136 --> 00:17:53,195 and it Was in my field area. 297 00:17:53,338 --> 00:17:54,828 We got some clothing together 298 00:17:54,973 --> 00:17:57,965 and We took the next flight up to Alaska. 299 00:18:01,080 --> 00:18:03,412 Our mission Was to assess the damage. 300 00:18:03,549 --> 00:18:06,518 And of course as a scientist l Was interested 301 00:18:06,652 --> 00:18:09,621 in trying to figure out the cause of this earthquake. 302 00:18:09,755 --> 00:18:11,916 UnknoWn to George at the time, 303 00:18:12,057 --> 00:18:15,823 understanding the cause Would have global implications. 304 00:18:17,196 --> 00:18:20,188 But his immediate problem Was just getting around; 305 00:18:20,332 --> 00:18:24,098 the earthquake had affected a vast and remote region. 306 00:18:26,405 --> 00:18:27,372 When We first came up, 307 00:18:27,506 --> 00:18:28,905 all We had heard Was that the roads 308 00:18:29,041 --> 00:18:30,235 and railroads Were cut 309 00:18:30,375 --> 00:18:33,003 and that there Was a great deal of landsliding 310 00:18:33,145 --> 00:18:36,546 and Wave damage in the coastal areas. 311 00:18:37,116 --> 00:18:39,880 There Was a big...Water out there, 312 00:18:40,018 --> 00:18:43,351 betWeen this island and that mainland over there. 313 00:18:43,489 --> 00:18:45,889 l said; 'oh, my gosh; tidal Wave', and l just kept running - 314 00:18:46,024 --> 00:18:47,992 l didn't even look back. 315 00:18:48,527 --> 00:18:50,825 Amongst all the stories of eye-Witnesses, 316 00:18:50,963 --> 00:18:53,090 confusing reports of sea-level changes 317 00:18:53,232 --> 00:18:55,223 Were also emerging. 318 00:18:55,367 --> 00:18:57,699 Some Witnesses claimed the sea level had dropped, 319 00:18:57,836 --> 00:19:00,464 others that it had risen. 320 00:19:03,575 --> 00:19:06,100 George's hunch Was that something fundamental 321 00:19:06,245 --> 00:19:08,440 had happened to the land itself, 322 00:19:08,580 --> 00:19:10,207 and that Working this out Would lead him 323 00:19:10,349 --> 00:19:12,817 to the cause of the earthquake. 324 00:19:15,387 --> 00:19:18,754 He decided to examine the shore-line in detail. 325 00:19:20,659 --> 00:19:24,026 This is What We had to do to get around this shore-line. 326 00:19:29,568 --> 00:19:34,096 And it Was here that he made his first remarkable discovery. 327 00:19:36,275 --> 00:19:40,302 This Water level is a little bit beloW mean high-tide. 328 00:19:43,782 --> 00:19:45,340 Mean high-tide normally reaches 329 00:19:45,484 --> 00:19:48,453 to about the top of this rock, 330 00:19:48,587 --> 00:19:50,851 and you can see these barnacles on the rock 331 00:19:50,989 --> 00:19:54,789 and seaWeed Which groW up to that level. 332 00:19:54,927 --> 00:19:57,452 Let me shoW you something fascinating noW. 333 00:19:59,231 --> 00:20:02,997 Here is a line of dead barnacles 334 00:20:03,135 --> 00:20:05,228 and this line is about six feet 335 00:20:05,370 --> 00:20:07,838 above the living barnacles. 336 00:20:17,282 --> 00:20:18,840 When l came here in 1964, 337 00:20:18,984 --> 00:20:21,544 some of these barnacles Were still alive. 338 00:20:22,854 --> 00:20:24,219 George realised that during 339 00:20:24,356 --> 00:20:26,324 the feW moments of the earthquake, 340 00:20:26,458 --> 00:20:29,791 the land here had been jacked up six feet. 341 00:20:32,064 --> 00:20:33,292 What Was more, George had found 342 00:20:33,432 --> 00:20:35,662 a Way to measure accurately land level changes 343 00:20:35,801 --> 00:20:39,100 over the Whole enormous area affected. 344 00:20:42,741 --> 00:20:45,608 He visited hundreds of small coves and inlets, 345 00:20:45,744 --> 00:20:48,235 folloWing the line of barnacles. 346 00:20:48,380 --> 00:20:50,610 That big... Wheel going doWn the track 347 00:20:50,749 --> 00:20:53,183 means it's all up and doWn, He ain't coming back, 348 00:20:53,318 --> 00:20:55,445 so l'm moving on, 349 00:20:55,587 --> 00:20:57,851 l'll soon be gone. 350 00:20:58,690 --> 00:21:01,056 You are flying too high for my little old sky, 351 00:21:01,193 --> 00:21:03,753 so l'm moving on. 352 00:21:04,296 --> 00:21:06,560 That big loud Whistle as it bleW and bleW, 353 00:21:06,698 --> 00:21:08,256 Said hello to the south land, 354 00:21:08,400 --> 00:21:11,130 We're coming to you When We're moving on, 355 00:21:11,637 --> 00:21:13,901 Oh hear my song... 356 00:21:14,039 --> 00:21:15,529 NoW there are thirty tWo feet 357 00:21:15,674 --> 00:21:19,667 above the level at Which barnacles live at the present time. 358 00:21:23,148 --> 00:21:26,117 Spent all of the summer of 1964 359 00:21:26,251 --> 00:21:28,617 and most of the summer of 1965 360 00:21:28,754 --> 00:21:30,483 studying a stretch of coast 361 00:21:30,622 --> 00:21:34,718 more than 500 miles from one end to the other. 362 00:21:35,727 --> 00:21:38,059 lt's to find my home, so please listen to me, 363 00:21:38,196 --> 00:21:39,629 'cause l got a pretty mamma.... 364 00:21:39,765 --> 00:21:41,357 Where the shore-line Was uplifted, 365 00:21:41,500 --> 00:21:45,027 plants soon colonised the neW land. 366 00:21:47,639 --> 00:21:49,903 Portage is about 270 degrees... 367 00:21:50,042 --> 00:21:51,703 But When he fleW north West, 368 00:21:51,843 --> 00:21:52,810 further inland, 369 00:21:52,944 --> 00:21:54,844 it Was a completely different story. 370 00:21:54,980 --> 00:21:56,914 ...go across Naked lsland... 371 00:21:57,049 --> 00:21:58,073 Before the earthquake, 372 00:21:58,216 --> 00:22:01,083 Portage had been a thriving rail stop. 373 00:22:01,219 --> 00:22:04,620 But George learned that it Was noW being flooded at high tides, 374 00:22:04,756 --> 00:22:08,624 and icebergs Were floating up the river into the toWn. 375 00:22:08,760 --> 00:22:09,749 We Were stood over there 376 00:22:09,895 --> 00:22:11,795 Where the railroad station used to be, 377 00:22:11,930 --> 00:22:13,830 and Watched these icebergs 378 00:22:13,965 --> 00:22:16,490 slam into the bar building and bounce off: 379 00:22:16,635 --> 00:22:19,900 they'd slam into the houses and go crunch. 380 00:22:20,038 --> 00:22:22,404 That night, the Water came in 381 00:22:22,541 --> 00:22:24,805 to the top of the bar 382 00:22:24,943 --> 00:22:26,035 Where people sat to drink, 383 00:22:26,178 --> 00:22:27,873 and Was clear up to there. 384 00:22:28,013 --> 00:22:31,676 And old guy that Worked or us stayed in the bar that night: 385 00:22:31,817 --> 00:22:34,081 the rest of us all fled across the street, 386 00:22:34,219 --> 00:22:36,915 and We all go back over to see if he's all right. 387 00:22:37,055 --> 00:22:39,751 And of course he Was; he Was drunk. 388 00:22:41,593 --> 00:22:43,254 George realised that in this region, 389 00:22:43,395 --> 00:22:47,832 land had gone doWn, nearly tWo metres at Portage. 390 00:22:48,667 --> 00:22:50,726 The subsequent inundation of sea Water, 391 00:22:50,869 --> 00:22:53,963 killed large tracts of pine forest. 392 00:22:59,511 --> 00:23:02,071 When George plotted his measurements on a map, 393 00:23:02,214 --> 00:23:05,081 he found that a striking picture emerged. 394 00:23:05,217 --> 00:23:06,707 Along the coastal regions, 395 00:23:06,852 --> 00:23:09,343 an area about the size of Great Britain 396 00:23:09,488 --> 00:23:13,720 had risen during the earthquake up to 12 metres, 397 00:23:14,159 --> 00:23:16,719 While further inland another vast area 398 00:23:16,862 --> 00:23:20,059 had gone doWn about tWo metres. 399 00:23:22,467 --> 00:23:23,365 That Was something 400 00:23:23,502 --> 00:23:27,700 that Was absolutely neW and different; 401 00:23:27,839 --> 00:23:29,101 nobody had ever seen anything like that 402 00:23:29,241 --> 00:23:32,506 before probably on the face of the earth. 403 00:23:36,014 --> 00:23:39,074 George Plafker had discovered movements of the earth's crust 404 00:23:39,217 --> 00:23:42,516 on a totally unprecedented scale, 405 00:23:42,654 --> 00:23:44,588 that accounted for the huge landslides 406 00:23:44,723 --> 00:23:46,953 and the tidal Waves. 407 00:23:47,426 --> 00:23:49,758 What he still had to explain Was Why parts 408 00:23:49,895 --> 00:23:54,389 of the Alaskan crust had risen, Whilst other parts had sunk. 409 00:23:55,000 --> 00:23:57,093 And the explanation he came up With 410 00:23:57,235 --> 00:24:00,500 changed our vieW of the earth for ever. 411 00:24:02,274 --> 00:24:05,209 When George Was Working on the geological effects 412 00:24:05,343 --> 00:24:08,005 of the Alaskan earthquake of 1964, 413 00:24:08,146 --> 00:24:10,910 We already kneW big tilts of the ground 414 00:24:11,049 --> 00:24:12,209 and movements of the ground, 415 00:24:12,350 --> 00:24:15,911 and indeed earthquakes Were the result of slip on faults, 416 00:24:16,054 --> 00:24:17,612 and perhaps the best example in the World 417 00:24:17,756 --> 00:24:21,954 that has been best studied is the San Andreas fault in California. 418 00:24:23,295 --> 00:24:26,321 And here We have a couple of rather nice slides, 419 00:24:26,465 --> 00:24:29,730 Where a large segment of the fault is slipping along, 420 00:24:29,868 --> 00:24:30,892 so quite naturally, 421 00:24:31,036 --> 00:24:33,402 George Was looking for a similar kind of structure, 422 00:24:33,538 --> 00:24:37,235 a steep break in the aearth's crust along the Alaskan region, 423 00:24:37,375 --> 00:24:40,572 to explain the 1964 earthquake. 424 00:24:42,247 --> 00:24:47,048 But in Alaska there Was no sign of a large fault cutting the surface. 425 00:24:48,453 --> 00:24:50,751 Despite all of our efforts, 426 00:24:50,889 --> 00:24:53,858 We didn't find such a fault. 427 00:24:53,992 --> 00:24:55,960 NoW this Was a major puzzle 428 00:24:56,094 --> 00:24:59,257 and something that bothered me for a long time. 429 00:25:01,233 --> 00:25:04,691 But then George started to look elseWhere. 430 00:25:08,940 --> 00:25:11,101 Finally, after much thinking about it, 431 00:25:11,243 --> 00:25:15,145 l realised that the fault We Were looking for 432 00:25:15,280 --> 00:25:18,078 actually underlays the entire region 433 00:25:18,216 --> 00:25:20,810 of uplifted subsidence, 434 00:25:20,952 --> 00:25:22,078 and that We couldn't see it 435 00:25:22,220 --> 00:25:26,054 because it came to the surface out to sea. 436 00:25:30,295 --> 00:25:34,197 George's insight Was that the fault Was underground, 437 00:25:34,332 --> 00:25:37,927 sloping gently beneath the entire region. 438 00:25:41,172 --> 00:25:43,003 Oceanographers had knoWn for some time 439 00:25:43,141 --> 00:25:46,633 about a mysterious deep trench in the sea floor 440 00:25:46,778 --> 00:25:49,713 about a hundred kilometres offshore. 441 00:25:49,848 --> 00:25:51,645 George Was convinced that this Was 442 00:25:51,783 --> 00:25:55,378 Where his gigantic fault reached the surface - 443 00:25:55,520 --> 00:25:57,420 under Water. 444 00:26:00,559 --> 00:26:01,958 So if l draW a cross-section of Alaska - 445 00:26:02,093 --> 00:26:03,958 l come from the north, do the land, 446 00:26:04,095 --> 00:26:07,155 across the volcano and doWn gradually, 447 00:26:07,299 --> 00:26:10,632 steeper and deeper, then doWn into a deep ocean trench, 448 00:26:10,769 --> 00:26:12,031 and l'll draW the sea 449 00:26:12,170 --> 00:26:16,266 in a blue Wavy colour like this. 450 00:26:16,408 --> 00:26:18,899 What George found, you remember, of course, 451 00:26:19,044 --> 00:26:22,207 Was that the great Alaskan earthquake of 1964 452 00:26:22,347 --> 00:26:25,248 Was produced on a fault plane dipping gently 453 00:26:25,383 --> 00:26:27,248 under Alaska like this, 454 00:26:27,385 --> 00:26:29,853 With this sense of motions, 455 00:26:29,988 --> 00:26:33,788 that is the underpart Was slipping doWn under Alaska in that Way. 456 00:26:33,925 --> 00:26:35,688 And of course this is very important because 457 00:26:35,827 --> 00:26:39,786 if one projects that fault out along its length, 458 00:26:39,931 --> 00:26:42,593 lo and behold, it projects to exactly the position 459 00:26:42,734 --> 00:26:44,031 of the oceanic trench. 460 00:26:44,169 --> 00:26:46,569 So We can connect the trench directly 461 00:26:46,705 --> 00:26:49,469 With this plane of earthquakes. 462 00:26:50,575 --> 00:26:54,534 A major fault like this Would have caused repeated earthquakes 463 00:26:55,747 --> 00:26:56,873 and George realised 464 00:26:57,015 --> 00:26:59,006 it Was What happened betWeen earthquakes 465 00:26:59,150 --> 00:27:01,084 as the crust Was squeezed 466 00:27:01,219 --> 00:27:02,743 that could explain Why some places 467 00:27:02,887 --> 00:27:06,379 had gone doWn While others had risen. 468 00:27:10,795 --> 00:27:12,285 l have here a model, 469 00:27:12,430 --> 00:27:14,864 very simplified representation 470 00:27:15,000 --> 00:27:18,492 of the continental margin of Alaska. 471 00:27:18,637 --> 00:27:21,128 This represents the fault. 472 00:27:21,272 --> 00:27:23,536 For several centuries betWeen earthquakes 473 00:27:23,675 --> 00:27:27,304 there is gradual compression 474 00:27:27,445 --> 00:27:31,142 and uplift of the area above that fault, 475 00:27:31,282 --> 00:27:34,217 and at the time of an earthquake it slips suddenly, 476 00:27:34,352 --> 00:27:37,947 causing uplift on the seaWard side, 477 00:27:39,157 --> 00:27:43,253 and subsidence in the area Where there Was a fault. 478 00:27:51,169 --> 00:27:54,764 And this land movement Was not a one-off event. 479 00:27:56,441 --> 00:27:57,271 When he looked, 480 00:27:57,409 --> 00:27:59,639 George found signs of past earthquakes 481 00:27:59,778 --> 00:28:02,144 engraved in the landscape. 482 00:28:02,280 --> 00:28:03,872 This series of steps Was created 483 00:28:04,015 --> 00:28:05,983 as the land Was repeatedly jacked 484 00:28:06,117 --> 00:28:08,381 out of the sea every feW hundred years 485 00:28:08,520 --> 00:28:11,216 by a sudden movement on the fault. 486 00:28:11,856 --> 00:28:12,948 But it Was What Was happening 487 00:28:13,091 --> 00:28:17,027 beneath the fault that Was really significant. 488 00:28:17,162 --> 00:28:19,722 George suggested that With this sense of motion, 489 00:28:19,864 --> 00:28:23,231 the Whole of the Pacific Ocean floor is slipping, 490 00:28:23,368 --> 00:28:26,929 floWing doWn along this inclined plane underneath Alaska. 491 00:28:27,072 --> 00:28:30,337 And of course the expression of this are intermittent earthquakes 492 00:28:30,475 --> 00:28:32,568 about every seven or eight hundred years. 493 00:28:32,711 --> 00:28:35,202 lf you keep on adding up each feW metres of slip 494 00:28:35,346 --> 00:28:36,608 that generates the earthquake 495 00:28:36,748 --> 00:28:38,648 then over a long period of geological time 496 00:28:38,783 --> 00:28:39,943 this Was suggesting 497 00:28:40,085 --> 00:28:42,519 the Whole Pacific Ocean floor Was floWing doWn 498 00:28:42,654 --> 00:28:46,385 along this inclined plane underneath Alaska. 499 00:28:50,195 --> 00:28:51,958 Only then did George Plafker 500 00:28:52,097 --> 00:28:54,531 and his colleagues realise the full significance 501 00:28:54,666 --> 00:28:57,794 of the ocean trench off the coast of Alaska. 502 00:28:59,571 --> 00:29:03,530 Because this trench circled virtually the Whole Pacific margin, 503 00:29:03,675 --> 00:29:07,441 it suggested that the entire floor of the Pacific Ocean 504 00:29:07,579 --> 00:29:10,639 Was sliding back beneath the surrounding continents, 505 00:29:10,782 --> 00:29:14,183 sinking back into the Earth's interior. 506 00:29:14,319 --> 00:29:18,346 And this Was just part of an even bigger picture. 507 00:29:21,025 --> 00:29:22,890 Geologists had already discovered 508 00:29:23,027 --> 00:29:24,995 that the sea floor Was being continually 509 00:29:25,130 --> 00:29:27,257 created along the mid-ocean ridge- 510 00:29:27,398 --> 00:29:28,695 the volcanic mountain chain 511 00:29:28,833 --> 00:29:31,324 that ran up the middle of the oceans. 512 00:29:31,469 --> 00:29:35,235 The ultimate fate of this sea floor Was obvious noW. 513 00:29:35,373 --> 00:29:38,001 As it Was being created in the middle of the oceans, 514 00:29:38,143 --> 00:29:43,103 so it Was being destroyed at the trenches at ocean margins 515 00:29:43,248 --> 00:29:47,651 in What scientists called subduction zones. 516 00:29:53,958 --> 00:29:56,927 And this Was happening all over the planet. 517 00:29:57,061 --> 00:29:58,528 Together the ocean trenches 518 00:29:58,663 --> 00:30:01,962 and the mid-ocean ridges formed a netWork of lines, 519 00:30:02,100 --> 00:30:04,898 boundaries that divided the globe into vast, 520 00:30:05,036 --> 00:30:09,063 sloWly moving regions - the plates. 521 00:30:16,347 --> 00:30:19,145 lt Was an extraordinary revelation - 522 00:30:19,284 --> 00:30:21,411 geologists suddenly realized 523 00:30:21,553 --> 00:30:26,820 that the entire surface of our World Was in constant motion. 524 00:30:29,661 --> 00:30:33,529 And so the theory of plate tectonics Was born, 525 00:30:33,665 --> 00:30:35,758 and scientists started thinking about the earth 526 00:30:35,900 --> 00:30:38,425 in a completely neW Way. 527 00:30:39,871 --> 00:30:42,931 And it's really quite an extraordinary idea, 528 00:30:43,074 --> 00:30:45,975 but remarkably simple. 529 00:30:46,110 --> 00:30:47,805 The surface of the earth consists 530 00:30:47,946 --> 00:30:49,914 of a number of rigid plates 531 00:30:50,048 --> 00:30:52,209 that are moving relative to each other: 532 00:30:52,350 --> 00:30:54,215 and this map here shoWs these plates 533 00:30:54,352 --> 00:30:56,445 in different colours. 534 00:30:56,588 --> 00:30:58,215 And the Pacific region forms 535 00:30:58,356 --> 00:31:01,587 a huge plate Which um is moving relative 536 00:31:01,726 --> 00:31:04,718 to the Australian plate in the NeW Zealand region, 537 00:31:04,863 --> 00:31:10,096 and sliding past the North American plate in California. 538 00:31:11,436 --> 00:31:14,337 The continents move With the plates. 539 00:31:14,472 --> 00:31:15,803 Throughout geological time, 540 00:31:15,940 --> 00:31:18,374 they have completely rearranged themselves, 541 00:31:18,509 --> 00:31:19,942 sometimes coming together 542 00:31:20,078 --> 00:31:22,103 and sometimes splitting apart, 543 00:31:22,247 --> 00:31:24,807 opening and closing oceans, 544 00:31:24,949 --> 00:31:28,316 re-shaping the face of the earth. 545 00:31:30,221 --> 00:31:33,247 What had begun ith a line of dead barnacles 546 00:31:33,391 --> 00:31:36,690 ended With a neW vieW of our planet. 547 00:31:37,862 --> 00:31:40,262 Plate tectonics suddenly arrived as a marvellous theory 548 00:31:40,398 --> 00:31:42,559 because it Was able to suddenly explain lots of things 549 00:31:42,700 --> 00:31:46,466 We Weren't able to explain many years ago. 550 00:31:52,911 --> 00:31:54,139 Back in Bolivia, 551 00:31:54,279 --> 00:31:57,112 scientists began using the theory of plate tectonics 552 00:31:57,248 --> 00:32:00,775 to explain the origin of the Ring of Fire. 553 00:32:02,353 --> 00:32:04,048 Leonore Hoke and the team 554 00:32:04,188 --> 00:32:06,122 believe that it can also throW neW light 555 00:32:06,257 --> 00:32:09,055 on the growth of the continents. 556 00:32:09,193 --> 00:32:11,388 They knoW that deep beneath their feet, 557 00:32:11,529 --> 00:32:15,488 ocean plate is sinking into the earth's interior. 558 00:32:15,633 --> 00:32:16,895 NoW it's very interesting 559 00:32:17,035 --> 00:32:21,028 because We have volcanoes round about 560 00:32:21,172 --> 00:32:23,834 in the position 561 00:32:23,975 --> 00:32:26,705 Where the subducting oceanic plate 562 00:32:26,844 --> 00:32:30,803 is 100 to 120 kilometres beloW the surface 563 00:32:30,949 --> 00:32:32,507 Where We are here noW. 564 00:32:32,650 --> 00:32:33,776 And that's Where We have volcanoes; 565 00:32:33,918 --> 00:32:36,113 and We knoW from looking at the volcanoes 566 00:32:36,254 --> 00:32:39,348 that they produce a lot of molten rock 567 00:32:39,490 --> 00:32:43,984 and they produce a lot of fluids like Water. 568 00:32:45,163 --> 00:32:48,223 Geologists suspect that some of this Water comes directly 569 00:32:48,366 --> 00:32:50,266 from the sinking ocean plate 570 00:32:50,401 --> 00:32:53,837 and may explain Why the volcanoes are here. 571 00:32:58,409 --> 00:33:00,639 Leonore plans to test this idea 572 00:33:00,778 --> 00:33:04,373 by collecting a sample from high on the volcano. 573 00:33:06,784 --> 00:33:09,480 Well, this is my blue barrel 574 00:33:09,620 --> 00:33:13,579 Which contains all the sample equipment Which l need, 575 00:33:14,459 --> 00:33:17,155 and there are all sorts of things in it like this gas mask 576 00:33:17,295 --> 00:33:19,991 Which protects me from noxious gases, 577 00:33:20,131 --> 00:33:24,090 funnels to collect gas bubbles With, 578 00:33:24,235 --> 00:33:28,535 it contains this tubing Which l need, 579 00:33:28,673 --> 00:33:33,508 and it contains these containers, 580 00:33:33,644 --> 00:33:35,942 and l pack them With at sea-level in NeW Zealand, 581 00:33:36,080 --> 00:33:38,139 oops, they pop When you open them 582 00:33:38,282 --> 00:33:40,716 because We are really at high altitude here. 583 00:33:40,852 --> 00:33:43,912 And here are these special glass containers 584 00:33:44,055 --> 00:33:48,754 um into Which l Will suck the gas they evacuated, 585 00:33:48,893 --> 00:33:51,521 and the gases Will tell me an awful lot about processes 586 00:33:51,662 --> 00:33:54,460 Which gave rise to formation of these volcanoes- 587 00:33:54,599 --> 00:33:57,830 volcanoes and processes Which happen at great depth. 588 00:34:02,206 --> 00:34:03,605 Are We ready then? 589 00:34:03,741 --> 00:34:05,299 Como si yama ...? 590 00:34:05,443 --> 00:34:06,239 Benito Velo 591 00:34:06,377 --> 00:34:08,345 Benito. Leonore. 592 00:34:08,479 --> 00:34:10,208 Benito . Se Catrin. 593 00:34:10,348 --> 00:34:11,713 Come stas? 594 00:34:11,849 --> 00:34:12,781 OK? 595 00:34:12,917 --> 00:34:15,943 lt's six a.m. on the Bolivian border With Chile. 596 00:34:16,087 --> 00:34:18,214 Leonore, Catrin and their guide 597 00:34:18,356 --> 00:34:21,621 are on their Way to their chosen sampling area. 598 00:34:25,263 --> 00:34:26,890 They're heading for the crater, 599 00:34:27,031 --> 00:34:29,727 the most dangerous place on the active volcano; 600 00:34:29,867 --> 00:34:32,199 lrruputuncu. 601 00:34:48,653 --> 00:34:51,520 The climbers are folloWing a rarely used footpath, 602 00:34:51,656 --> 00:34:55,251 made by locals to collect sulphur from the summit. 603 00:34:58,930 --> 00:35:02,229 They are climbing to nearly 6000 metres. 604 00:35:04,068 --> 00:35:05,729 At this height oxygen levels 605 00:35:05,870 --> 00:35:09,328 have almost halved making it difficult to breathe. 606 00:35:12,743 --> 00:35:13,903 lt's hard Work isn't it? 607 00:35:14,045 --> 00:35:16,809 Yeah. Biting Wind. 608 00:35:16,948 --> 00:35:19,974 Sulphurous smell's getting stronger as Well. 609 00:35:20,118 --> 00:35:22,746 Well, We're getting closer to the fumarole. 610 00:35:22,887 --> 00:35:25,651 Yup. Another hour or so. 611 00:35:25,790 --> 00:35:27,815 Brilliant vieW. 612 00:35:28,860 --> 00:35:30,259 That's really the reWard of it, isn't it? 613 00:35:30,394 --> 00:35:32,726 Yeah. lts' amazing. 614 00:35:32,864 --> 00:35:35,230 Feel like a bird up here. 615 00:35:38,870 --> 00:35:41,532 The higher they go, the steeper the climb, 616 00:35:41,672 --> 00:35:46,405 as the sticky volcanic rock has built up the slopes of the crater. 617 00:35:50,214 --> 00:35:54,651 After 4 hours they're Within sight of their goal. 618 00:36:45,469 --> 00:36:49,235 This is the solid material that the volcano's made from. 619 00:36:49,373 --> 00:36:53,173 lt's dark, almost black. 620 00:36:53,311 --> 00:36:56,280 But covering all these rocks is sulphur, 621 00:36:56,414 --> 00:36:58,006 Which is coming from the gases 622 00:36:58,149 --> 00:37:01,585 that are coming up from the craters behind me. 623 00:37:01,719 --> 00:37:04,711 Beautiful yelloW crystalline material. 624 00:37:04,855 --> 00:37:07,915 The gases are also containing Water, 625 00:37:08,059 --> 00:37:11,358 and that Water is pervasively reacting 626 00:37:11,495 --> 00:37:14,293 With the rock, and changing it, 627 00:37:14,432 --> 00:37:18,630 so We get this crumbly White material. 628 00:37:21,505 --> 00:37:22,631 lt's this Water, 629 00:37:22,773 --> 00:37:25,333 together With other gases rising through the crater, 630 00:37:25,476 --> 00:37:28,536 that Leonore has come to collect. 631 00:37:30,514 --> 00:37:32,573 l'm taking a condensate sample; 632 00:37:32,717 --> 00:37:35,242 that means l'm collecting the steam 633 00:37:35,386 --> 00:37:37,752 and l guide it through this glass container 634 00:37:37,888 --> 00:37:40,015 Which is immersed in snoW, 635 00:37:40,157 --> 00:37:43,684 and that cools the steam, 636 00:37:43,828 --> 00:37:45,955 and l'm collecting the Water at the bottom of it, 637 00:37:46,097 --> 00:37:47,325 and you Will see later 638 00:37:47,465 --> 00:37:51,401 on there's quite a lot of Water in this steam. 639 00:37:52,003 --> 00:37:54,233 l'm having a look noW hoW much Water there is; 640 00:37:54,372 --> 00:37:56,772 l dig it out of the snoW. 641 00:38:01,279 --> 00:38:03,645 lt's great to get out of that 642 00:38:04,682 --> 00:38:06,877 hot steam; it's hundred and tWenty degrees. 643 00:38:07,018 --> 00:38:10,579 But What l've collected here is some Water; 644 00:38:10,721 --> 00:38:12,746 you can see it in here. 645 00:38:12,890 --> 00:38:15,484 There's quite a lot coming out of this fumarole. 646 00:38:15,626 --> 00:38:18,652 NoW the chemistry of this Water Will tell us 647 00:38:18,796 --> 00:38:20,491 Where this Water's coming from 648 00:38:20,631 --> 00:38:23,691 and it Will be analysed back at the lab. 649 00:38:33,110 --> 00:38:34,168 There's yelloW all over it. 650 00:38:34,312 --> 00:38:37,076 Covered With sulphur. ...your eyes and things. 651 00:38:37,214 --> 00:38:39,512 lt Was kind of like Hell. 652 00:38:39,650 --> 00:38:43,416 The devil Was about to pop his head out any minute. 653 00:38:44,955 --> 00:38:47,253 OK, time to go. 654 00:38:48,926 --> 00:38:50,826 Mm, it's still Warm. 655 00:38:54,398 --> 00:38:56,229 Back in Wellington, NeW Zealand, 656 00:38:56,367 --> 00:39:00,030 Leonore heads straight for her laboratory. 657 00:39:10,114 --> 00:39:12,275 Here l've got the sample 658 00:39:12,416 --> 00:39:16,216 l collected on top of active volcano in Bolivia, 659 00:39:16,354 --> 00:39:18,788 so let's see What's in it. 660 00:39:19,256 --> 00:39:21,816 She's about to measure the composition of the sample 661 00:39:21,959 --> 00:39:24,359 to get an insight into the events taking place 662 00:39:24,495 --> 00:39:26,963 deep beloW the volcano. 663 00:39:32,636 --> 00:39:35,196 You can measure the different gas components 664 00:39:35,339 --> 00:39:38,672 in the sample, and it contains helium, 665 00:39:38,809 --> 00:39:40,834 it contains argon, it contains CO2, 666 00:39:40,978 --> 00:39:42,570 it contains nitrogen 667 00:39:42,713 --> 00:39:45,011 and many other gas components. 668 00:39:45,149 --> 00:39:46,980 But it's the concentratioan of nitrogen 669 00:39:47,118 --> 00:39:48,779 Which catches her attention; 670 00:39:48,919 --> 00:39:51,444 it goes almost off the scale. 671 00:39:54,125 --> 00:39:55,092 That's good. 672 00:39:55,226 --> 00:39:59,185 l have quite a high signal coming from the nitrogen. 673 00:40:02,800 --> 00:40:05,462 Nitrogen is the most common gas in air. 674 00:40:05,603 --> 00:40:08,299 But the proportion in the sample is far too high; 675 00:40:08,439 --> 00:40:11,567 it suggests a completely different source. 676 00:40:15,413 --> 00:40:19,247 Leonara turns her attention to the Water in the sample. 677 00:40:19,850 --> 00:40:21,875 We can also measure the isotypes 678 00:40:22,019 --> 00:40:23,577 of these gas components 679 00:40:23,721 --> 00:40:27,020 by using a mass petrometer 680 00:40:29,827 --> 00:40:31,795 By analysing the atoms in the Water, 681 00:40:31,929 --> 00:40:36,298 Leonore is hoping to test a startling idea. 682 00:40:38,869 --> 00:40:40,530 She suspects that some of the Water 683 00:40:40,671 --> 00:40:43,367 in the sample might come from the sea. 684 00:40:43,507 --> 00:40:46,067 lf so, it Would support her groWing conviction 685 00:40:46,210 --> 00:40:49,509 that the nitrogen could be coming from dead marine organisms 686 00:40:49,647 --> 00:40:51,239 knoWn to be nitrogen rich, 687 00:40:51,382 --> 00:40:53,816 buried in the sea floor. 688 00:40:56,554 --> 00:40:58,112 Could the flask from Bolivia 689 00:40:58,255 --> 00:41:01,315 contain a sample of the Pacific Ocean? 690 00:41:01,459 --> 00:41:04,553 The hydrogen is very close 691 00:41:04,695 --> 00:41:07,129 to the hydrogen isotopes of sea Water. 692 00:41:07,264 --> 00:41:09,357 So that suggests that some component 693 00:41:09,500 --> 00:41:12,663 Within that Water is probably sea Water. 694 00:41:13,337 --> 00:41:14,304 So We can say from that 695 00:41:14,438 --> 00:41:18,397 that a lot of that nitrogen is biogenic nitrogen, 696 00:41:18,542 --> 00:41:21,033 produced in ocean sediments 697 00:41:21,178 --> 00:41:24,670 and released during the subduction process. 698 00:41:28,018 --> 00:41:29,576 So the journey up the volcano 699 00:41:29,720 --> 00:41:32,416 has yielded an amazing result - 700 00:41:32,556 --> 00:41:35,684 high up at the summit are traces of marine life 701 00:41:35,826 --> 00:41:38,090 and thePacific Ocean itself, 702 00:41:38,229 --> 00:41:39,423 Which have completed a long 703 00:41:39,563 --> 00:41:42,498 and extraordinary journey through the Earth. 704 00:41:42,633 --> 00:41:43,565 Good climb? 705 00:41:43,701 --> 00:41:44,690 Excellent. 706 00:41:44,835 --> 00:41:48,271 The Whole story's contained in one glass flask. 707 00:41:50,574 --> 00:41:52,667 You suffered With me! 708 00:41:54,144 --> 00:41:56,112 And of course a large part of this cyclic process 709 00:41:56,247 --> 00:41:57,771 explains the origin - origins of the continents 710 00:41:57,915 --> 00:42:00,383 because We noW see that lovely link 711 00:42:00,518 --> 00:42:01,951 betWeen the origin of volcanoes 712 00:42:02,086 --> 00:42:03,451 and the oceanic trench. 713 00:42:03,587 --> 00:42:04,952 lt's a beautifully linked system. 714 00:42:05,089 --> 00:42:07,717 We noW have the picture of this flux of Wet rock, 715 00:42:07,858 --> 00:42:10,622 oceanic material coming into the subduction zone, 716 00:42:10,761 --> 00:42:12,251 carrying a lot of Water With it, 717 00:42:12,396 --> 00:42:13,590 getting hotter and hotter 718 00:42:13,731 --> 00:42:18,031 and eventually it gets so hot that the Water is expelled... 719 00:42:19,537 --> 00:42:23,064 ...and that Water Will arise into the mantle 720 00:42:23,207 --> 00:42:25,539 above and Will act like anti-freeze; 721 00:42:25,676 --> 00:42:27,803 it Will trigger melting. 722 00:42:27,945 --> 00:42:31,506 So Water is the key to the Ring of Fire. 723 00:42:31,649 --> 00:42:34,015 As the ocean floor sinks into the earth, 724 00:42:34,151 --> 00:42:37,552 Water is squeezed out of the rocks. 725 00:42:37,688 --> 00:42:40,213 Like scattering salt on an icy road, 726 00:42:40,357 --> 00:42:42,848 the Water reduces the melting point 727 00:42:42,993 --> 00:42:44,392 of the surrounding rocks 728 00:42:44,528 --> 00:42:47,292 and so they start to melt. 729 00:42:48,365 --> 00:42:50,697 This molten rock rises to the surface, 730 00:42:50,834 --> 00:42:53,962 to erupt as a line of volcanoes. 731 00:43:02,179 --> 00:43:05,910 But these volcanoes are like the tip of an iceberg. 732 00:43:07,618 --> 00:43:08,915 Only a small proportion 733 00:43:09,053 --> 00:43:11,988 of the molten rockever reaches the surface. 734 00:43:12,122 --> 00:43:14,818 Most of it is building the continental crust 735 00:43:14,959 --> 00:43:17,223 beneath our feet. 736 00:43:18,395 --> 00:43:21,421 The surface volcanoes are merely the surface manifestation 737 00:43:21,565 --> 00:43:26,298 of a huge process of the addition of neW hot material to the crust. 738 00:43:26,437 --> 00:43:27,927 And if this has been going on 739 00:43:28,072 --> 00:43:29,437 for some considerable period of time, 740 00:43:29,573 --> 00:43:31,097 Which We knoW it has, 741 00:43:31,241 --> 00:43:33,732 you can actually make very large amounts of continental crust 742 00:43:33,877 --> 00:43:35,538 in this Way. 743 00:43:41,518 --> 00:43:44,180 There's a huge volume of volcanic material 744 00:43:44,321 --> 00:43:46,755 being added to the crust. 745 00:43:48,392 --> 00:43:51,122 BeloW us, We can imagine more molten rock 746 00:43:51,261 --> 00:43:54,662 ponding underneath you at some level. 747 00:43:57,835 --> 00:43:59,462 As you drive along, you're Witnessing 748 00:43:59,603 --> 00:44:01,571 the growth of continental crusts. 749 00:44:01,705 --> 00:44:04,003 lt's quite an exciting thought. 750 00:44:04,141 --> 00:44:06,371 Here is a place Where for millions of years 751 00:44:06,510 --> 00:44:08,239 the continent has been groWing, 752 00:44:08,379 --> 00:44:09,971 and it's going to continue probably 753 00:44:10,114 --> 00:44:13,311 for many more millions of years. 754 00:44:16,020 --> 00:44:19,421 But as the plates have moved through out geological time, 755 00:44:19,556 --> 00:44:20,921 the places Where the continents 756 00:44:21,058 --> 00:44:24,118 groW have shifted over the Earth. 757 00:44:26,063 --> 00:44:27,997 Britain's ancient crust Was built up 758 00:44:28,132 --> 00:44:30,191 in the same Way by volcanoes - 759 00:44:30,334 --> 00:44:33,565 450 million years ago. 760 00:44:33,704 --> 00:44:35,638 As MattheW ThirlWall explains 761 00:44:35,773 --> 00:44:38,105 in the Lake District. 762 00:44:43,580 --> 00:44:44,911 Everything We see over here 763 00:44:45,049 --> 00:44:48,382 Was produced by big eruptions. 764 00:44:49,319 --> 00:44:51,514 BeloW us, there's something like eight thousand metres 765 00:44:51,655 --> 00:44:53,623 of volcanic rock. 766 00:44:53,757 --> 00:44:56,783 We can tell from the andesitic composition of the rocks, 767 00:44:56,927 --> 00:44:59,487 that there Was almost certainly a subduction zone 768 00:44:59,630 --> 00:45:02,224 beneath the Lake District, With an ocean to the north, 769 00:45:02,366 --> 00:45:04,391 and an oceanic plate coming doWn 770 00:45:04,535 --> 00:45:06,366 beneath the Lake District, beneath Wales, 771 00:45:06,503 --> 00:45:08,300 beneath lreland and so on. 772 00:45:08,439 --> 00:45:12,603 And the crust in this area almost certainly 773 00:45:12,743 --> 00:45:16,406 greW as a response to that subduction. 774 00:45:17,347 --> 00:45:19,781 WorldWide, the composition 775 00:45:19,917 --> 00:45:22,818 of the continental crust is andesitic, 776 00:45:22,953 --> 00:45:25,046 right the Way back through time. 777 00:45:25,189 --> 00:45:28,920 Subduction zones Were the sites of continental crust formation, 778 00:45:29,059 --> 00:45:30,993 not just at the present day at the Ring of Fire, 779 00:45:31,128 --> 00:45:32,288 but right the Way back 780 00:45:32,429 --> 00:45:35,557 until the earliest parts of earth history. 781 00:45:39,136 --> 00:45:40,899 As the continents have groWn, 782 00:45:41,038 --> 00:45:43,563 another legacy has been left behind; 783 00:45:43,707 --> 00:45:48,337 the mineral Wealth With Which We have forged civilisation. 784 00:45:49,913 --> 00:45:52,541 The Cerro Rico itself used to be an active volcano 785 00:45:52,683 --> 00:45:55,709 some 16 million years ago. 786 00:45:59,189 --> 00:46:01,657 And the much older volcanoes in the Lake District 787 00:46:01,792 --> 00:46:05,455 have also brought up their oWn rich dividend; 788 00:46:06,497 --> 00:46:08,089 copper. 789 00:46:08,232 --> 00:46:09,290 ln the 19th century, 790 00:46:09,433 --> 00:46:11,128 this area provided much of the copper 791 00:46:11,268 --> 00:46:14,704 for the burgeoning lndustrial Revolution. 792 00:46:16,073 --> 00:46:17,631 The link betWeen volcanoes 793 00:46:17,775 --> 00:46:20,335 and mineral Wealth is another cvonsequence 794 00:46:20,477 --> 00:46:23,503 of Water moving Within the earth. 795 00:46:23,647 --> 00:46:26,241 The connection is that the hot rocks 796 00:46:26,383 --> 00:46:28,408 at depth mobilise Water, 797 00:46:28,552 --> 00:46:32,886 and that Water circulates around the hot rocks, dissolves, 798 00:46:33,023 --> 00:46:36,220 leaches metals from the volcanic rocks, 799 00:46:36,360 --> 00:46:38,521 forces cracks up to the surface, 800 00:46:38,662 --> 00:46:41,426 transports the metals up in these cracks, 801 00:46:41,565 --> 00:46:44,056 and then deposits them as the pressure drops. 802 00:46:44,201 --> 00:46:46,135 lt's really luckythat that's What's actually happened 803 00:46:46,270 --> 00:46:49,797 because if the metals Were not deposited in these veins 804 00:46:49,940 --> 00:46:52,431 it Would take something like the Whole mountainside 805 00:46:52,576 --> 00:46:56,205 to Work to produce a single copper pipe. 806 00:46:56,346 --> 00:47:00,180 The volcanoes provide the Workable deposits. 807 00:47:06,690 --> 00:47:08,089 The people of the Cerro Rico 808 00:47:08,225 --> 00:47:11,319 have long believed the silver is a gift from Patja Mama 809 00:47:11,461 --> 00:47:13,793 their god of the earth. 810 00:47:15,833 --> 00:47:18,393 ln some Ways, they've been proved right. 811 00:47:18,535 --> 00:47:20,059 Scientists noW see hoW, 812 00:47:20,204 --> 00:47:22,035 as the plates of the earth move, 813 00:47:22,172 --> 00:47:24,470 creating the land on Which We live, 814 00:47:24,608 --> 00:47:28,305 our planet also yields up its Wealth.